A guy who lives next to the sports fields moved in recently with his 3 year old, unaltered, at least 90lb male GSD. Prior to, he had been living on a farm, the dog had the run of acres of farmland, he said he's been to classes, and the dog was limited in where he would go.

I don't like that dog, he is a beauty, but a real jerk. He is obviously under socialized, domineering, and easily provoked by anything, We have met numerous times, and every time, his dog begins and ends up aggressively behaving towards mine, pinning, growling, barking, lunging. Take what you will from this, but I have a hunch it is because he did not have the positive exposure and socialization that is important for all dogs.